This invention relates to connector assemblies for integrated circuit chips and, more particularly, to an improved electrical contact for use therein.
When designing connector assemblies for use with integrated circuit chips, different requirements for the contact element, which provides an electrical path between the chip and a printed circuit board on which the connector assembly is mounted, must be met. One requirement is that the portion of the contact which interfaces with the chip carrier be able to sustain a relatively large deflection in order to accommodate manufacturing dimensional variations or tolerances between individual chip packages. Such packages may contain a single IC chip or a number of them forming a subassembly. It is not unusual, at the present time, to have a variation of as much as 0.030 inch between the minimum and maximum dimensions of component chip packages from different manufacturers. At the same time, the contact force over that range must remain within acceptable limits. Thus, a relatively flat force/deflection curve is desirable. By way of example, in the case when the electrical contact is tin plated, the contact force should be approximately 220 grams for the minimum deflection of the contact and approximately 400 grams for the maximum deflection of the contact. This imposes certain requirements on the spring which generates the contact force. However, the space in which a spring of such compliance is to be designed must be small for a number of reasons. A first reason is that the high cost of material requires economy of size. A second reason is that electrical requirements dictate a short electrical path to minimize self-inductance in the contact.
Opposing these requirements is the known physical effect that a large deflection of metal usually results in a permanent, or plastic, deformation of the metal. If, however, a straight beam, by way of example, is to be deflected the required distance and stay within its elastic limit (i.e., a deformation magnitude within which the part will totally recover to its original position after removal of the deforming force) such a beam would have to be relatively long and would not satisfy the electrical length or space requirements.
It is therefore a primary object of this invention to provide a contact of the type described wherein a relatively short beam is deflected and the relatively large deflection of that short beam is changed into a relatively small deflection of a spring thereby permitting the spring to stay within its elastic limit.
It is another object of this invention to provide such a contact as a monolithic element.